Issues of storing and querying XML data, and other semi-structured data, have been studied extensively recently. Although there are efforts to build a repository for semi-structured data on object-oriented database systems or “native” structured language systems. Storing and querying the semi-structured data over relational database management systems (RDBMS) is becoming a common practice pursued by both researchers and database vendors.
There are typically several options of how to map semi-structured data stored in a particular configuration into relational databases. Much work for storing semi-structured data in relational database systems have provided various solutions for mapping the semi-structured data into relational tables (either by storing the semi-structured data in relational databases by a specific mapping approach using a fixed mapping method, or by leaving the user to specify the mapping schema). However, those approaches may not generate an efficient semi-structured data storage for an expected set of queries, and as such typically result in low performance for arbitrary semi-structured data and workload. Thus, it would be beneficial to provide a way to improve mapping of the semi-structured data into relational databases.